Bonding or adhesion of fluoroelastomers to metal, ceramic or glass substrates is important for some end use applications such as automotive shaft seals. Conventional fluoroelastomers comprising copolymerized units of vinylidene fluoride (VF2), hexafluoropropylene (HFP) and, optionally, tetrafluoroethylene (TFE) are typically bonded to metals by use of a silane, particularly an amino-silane primer.
Recently it has become desirable to employ in automotive applications fluoroelastomer seals which are particularly resistant to attack by basic fluids. Examples of such base-resistant fluoroelastomers include, but are not limited to 1) fluoroelastomers containing copolymerized units of tetrafluoroethylene and propylene (P); and 2) fluoroelastomers containing copolymerized units of ethylene (E), tetrafluoroethylene and a perfluoro(alkyl vinyl ether) (PAVE). These fluoroelastomers may also contain copolymerized units of vinylidene fluoride or a cure site monomer. When copolymerized units of vinylidene fluoride are present in the fluoroelastomer, the level is preferably less than about 10 weight percent in order to optimize resistance of the fluoroelastomer to attack by base.
Base resistant fluoroelastomers are more difficult to bond to metal, ceramic or glass substrates than are conventional fluoroelastomers. The widely used amino-silane class of primers are largely ineffective by themselves. EP 0617084 B1 (Grootaert et al.) discloses base-resistant TFE/P/VF2 fluoroelastomer compositions which contain a fluoroaliphatic sulfonyl compound. Such compositions, when used with an amino-silane primer, have improved adhesion to metal surfaces. JP 6-248115 (Kaneko et al.) discloses epoxy-silane primer compositions for bonding base-resistant TFE/P/VF2 fluoroelastomers to metal surfaces.
It would be desirable to further improve the adhesion of base-resistant fluoroelastomers to metal, ceramic or glass substrate surfaces, especially for fluoroelastomers containing no copolymerized vinylidene fluoride.